A recent analysis by Lionbridge found that while none of the four major carriers is 100 percent accurate at identifying spam and scam calls, some are better than others. And T-Mobile is best overall.

For the analysis, Lionbridge got a robocall service to place 8,000 calls to eight mobile devices: one Android device and one Apple device for each of the four major carriers. These calls came from more than 100 unique phone numbers per day.

The total shares of those calls that a carrier was able to identify as scam/fraud or spam/telemarketing calls — or for which the carrier was able to accurately provide a caller ID — varied widely:

T-Mobile: 91 percent

Verizon: 65 percent

Sprint: 51 percent

AT&T: 25 percent

Breakdown of findings

Looking specifically at known and verified scam/fraud numbers, T-Mobile performed far better than any other provider, identifying 90 percent of such calls. AT&T came in second here, identifying 14 percent of these calls.

Looking at known and verified spam/telemarketing calls, however, AT&T performed best, identifying 50 percent of such calls. T-Mobile came in close second, identifying 47 percent of those calls.

With verified safe consumer and business numbers, T-Mobile and Verizon tied, each providing caller IDs for 78 percent of such numbers. Sprint closely followed with 73 percent.

Stopping robocalls

Telecommunications companies — which are regulated by the U.S. Federal Communications Commission — may be limited in their ability to fight robocalls. It was only a few months ago that the FCC started allowing voice service providers to proactively block calls that are likely to be fraudulent.

Specifically, the FCC voted to allow providers to block calls that appear to be from certain invalid phone numbers, such as numbers that aren’t meant to dial out or numbers that have nonexistent area codes. This practice is known as “spoofing” — making it appear as if a call is coming from a different number.

At the same time, however, providers must be wary of blocking lawful calls.

Also, illegal robocalls are inherently tough to combat because the people behind them obviously aren’t above illegal tactics.